Improving nitrogen fertilization in rice by sitespecific N management. A review

Abstract

Excessive nitrogen (N) application to rice (Oryza sativa L.) crop in China causes environmental pollution, increases the cost of rice farming, reduces grain yield and contributes to global warming. Scientists from the International Rice Research Institute have collaborated with partners in China to improve rice N fertilization through site-specific N management (SSNM) in China since 1997. Field experiments and demonstration trials were conducted initially in Zhejiang province and gradually expanded to Guangdong, Hunan, Jiangsu, Hubei and Heilongjiang provinces. On average, SSNM reduced N fertilizer by 32% and increased grain yield by 5% compared with farmers' N practices. The yield increase was associated with the reduction in insect and disease damage and improved lodging resistance of rice crop under the optimal N inputs. The main reason for poor fertilizer N use efficiency of rice crop in China is that most rice farmers apply too much N fertilizer, especially at the early vegetative stage. We observed about 50% higher indigenous N supply capacity in irrigated rice fields in China than in other major rice-growing countries. Furthermore, yield response of rice crop to N fertilizer application is low in China, around 1.5 t ha −1 on average. However, these factors were not considered by rice researchers and extension technicians in determining the N fertilizer rate for recommendation to rice farmers in China. After a decade of research on SSNM in China and other Asian rice-growing countries, we believe SSNM is a matured technology for improving both fertilizer N use efficiency and grain yield of rice crop. Our challenges are to further simplify the procedure of SSNM and to convince policy-makers of the effectiveness of this technology in order to facilitate a wider adoption of SSNM among rice farmers in China.

Effects of Dense Planting with Less Basal N Fertilization on Rice Yield, N Use Efficiency and Greenhouse Gas Emissions

“…Reduction in N application usually promotes NUE especially for PFPN (Peng et al, 2010). The results of present study also exhibited that PFPN significantly increased as N rate reduced (Fig.…”

“…Moreover, Bhatia et al (2012) suggested a 12.5% reduction in N application during early vegetative stage could increase rice yield. These studies clearly demonstrated a moderate reduction in basal N application rate rice cropping innovation for higher NUE (Peng et al, 2010). Therefore, dense planting with less N application at early growing stage (e.g.…”

“…Most of these studies described the frequently yield losses caused by sparse planting (Tsujimoto et al, 2009;Ye et al, 2012;Huang et al, 2013), (Peng et al, 2010) in rice production of China. Present study explicitly emphasized the effect of planting density with less basal N application to develop cropping mode with at least high yield and NUE, or reduce area-and yield-scaled GHG emissions in rice field.…”

“…Thus, dense planting can be good approach to get further increases in rice yield Zhao et al, 2013;Huang et al, 2013), especially for the mechanical rice transplanting, which will be dominant in rice cropping areas (CMA, 2011). Meanwhile, many improved N managements have been made to increase NUE for rice cropping systems (Dobermann et al, 2002;Peng et al, 2010;Rehman et al, 2013;Sui et al, 2013). For example, Peng et al (2006) found that 30% reduction in N application during the early vegetative stage could double agronomic NUE without obvious reduction in rice yield compared to the farmers' practice in China.…”

Changes in Grain Yield and Root Morphology and Physiology of Mid-Season Rice in the Yangtze River Basin of China During the Last 60 Years

“…Increase in fertilizer nutrient input, especially nitrogen fertilizer, has contributed significantly to the improvement of crop yields (Cassman et al, 2003). China's national average nitrogen rate for rice was 193 kg ha −1 in 2006 (Peng et al, 2010). Nitrogen rates are ranged from 150 to 250 kg ha −1 , depending on rice planting areas (Wang et al, 2001;Peng et al, 2006).…”